Description

Copyright 2006

Dimensions: 7x9-1/4

Pages: 624

Edition: 1st

Book

ISBN-10: 0-13-185515-8

ISBN-13: 978-0-13-185515-1

eBook (Watermarked)

ISBN-10: 0-13-205523-6

ISBN-13: 978-0-13-205523-9

Linux is a fast-growing operating system with power and appeal, and enterprises worldwide are quickly adopting the system to utilize its benefits. But as with all operating systems, performance problems do occur causing system administrators to scramble into action. Finally, there is a complete reference for troubleshooting Linux–quickly! Linux Troubleshooting for System Administrators and Power Users is THE book for locating and solving problems and maintaining high performance in Red Hat® Linux and Novell® SUSE® Linux systems.

This book not only teaches you how to troubleshoot Linux, it shows you how the system works–so you can attack any problem at its root. Should you reinstall if Linux does not boot? Or can you save time by troubleshooting the problem? Can you enhance performance when Linux hangs or runs slowly? Can you overcome problems with printing or accessing a network? This book provides easy-to-follow examples and an extensive look at the tools, commands, and scripts that make Linux run properly.

A troubleshooting guide for all Linux users: Focuses on common problems with start-up, printing, login, the network, security, and more

Gone are the days of searching online for solutions that are out of date and unreliable. Whether you are a system admin, developer, or user, this book is an invaluable resource for ensuring that Linux runs smoothly, efficiently, and securely.

Table of Contents

Chapter 5 Adding New Storage via SAN with Reference to PCMCIA and USB 159

Chapter 6 Disk Partitions and Filesystems 185

Chapter 7 Device Failure and Replacement 229

Chapter 8 Linux Processes: Structures, Hangs, and Core Dumps 253

Chapter 9 Backup/Recovery 285

Chapter 10 cron and at 315

Chapter 11 Printing and Printers 345

Chapter 12 System Security 383

Chapter 13 Network Problems 423

Chapter 14 Login Problems 495

Chapter 15 X Windows Problems 527

Index 551

Preface

My good friend, James Kirkland, sent me an instant message one day asking if I
wanted to write a Linux troubleshooting book with him. James has been heavily
involved in Linux at the HP Response Center for several years. While troubleshooting
Linux issues for customers, he realized there was not a good troubleshooting reference
available. I remember a meeting discussing Linux troubleshooting. Someone asked
what the most valuable Linux troubleshooting tool was. The answer was immediate.
Google. If you have ever spent time trying to find a solution for a Linux problem,
you know what that engineer was talking about. A wealth of great Linux information
can be found on the Internet, but you can't always rely on this strategy. Some
of the Linux information is outdated. A lot of it can't be understood without
a good foundation of subject knowledge, and some of it is incorrect. We wanted
to write this book so the Linux administrator will know how Linux works and how
to approach and resolve common issues. This book contains the information we wish
we had when we started troubleshooting Linux.

Greg and Chris are identical twins and serious Linux hobbyists. They have been
Linux advocates within HP for years. Yes, they both run Linux on their laptops.
Chris is a member of the Superdome Server team (http://www.hp.com/products1/servers/scalableservers/superdome/index.html).
Greg works for the XP storage team (http://h18006.www1.hp.com/storage/xparrays.html).
Their Linux knowledge is wide and deep. They have worked through SAN storage
issues and troubleshot process hangs, Linux crashes, performance issues, and
everything else for our customers, and they have put their experience into the
book.

I am a member of the HP escalations team. I've primarily spent my time resolving
HPUX issues. I've been a Linux hobbyist for a few years, and I've started working
Linux escalations, but I'm definitely newer to Linux than the rest of the team.
I try to give the book the perspective of someone who is fairly new to Linux.
I tried to remember the questions I had when I first started troubleshooting
Linux issues and included them in the book. We sincerely hope our effort is
helpful to you.

Dave Carmichael

Chapter Summaries

These chapter summaries will give you an idea of how the book is organized and
a bit of an overview of the content of each chapter.

Chapter 1: System Boot, Startup, and Shutdown Issues
Chapter 1 discusses the different subsystems that comprise Linux startup. These
include the bootloaders GRUB and LILO, the init process, and the rc startup
and shutdown scripts. We explain how GRUB and LILO work along with the important
features of each. The reader will learn how to boot when there are problems
with the bootloader. There are numerous examples. We explain how init works
and what part it plays in starting Linux. The rc scripts are explained in detail
as well. The reader will learn how to boot to single user mode, emergency mode,
and confirm mode. Examples are included of using a recovery CD when Linux won't
boot from disk.

Chapter 2: System Hangs and Panics
This chapter explains interruptible and non-interruptible OS hangs, kernel panics,
and IA64 hardware machine checks. A Linux hang takes one of two forms. An interruptible
hang is when Linux seems frozen but does respond to some events, such as a ping
request. Non-interruptible hangs do not respond to any actions. We show how
to use the Magic SysReq keystroke to generate a stack trace to troubleshoot
an interruptible hang. We explain how to force a panic when Linux is in a non-interruptible
hang. An OS panic is a voluntary shutdown of the kernel in response to something
unexpected. We discuss how to obtain a panic dump from Linux. The IA64 architecture
dump mechanism is also explained.

Chapter 3: Performance Tools
In Chapter 3, we explain how to use some of the most popular Linux performance
tools including top, sar, vmstat, iostat, and free. The examples show common
syntaxes and options. Every system administrator should be familiar with these
commands.

Chapter 4: Performance
Chapter 4 discusses different approaches to isolating a performance problem.
As with the majority of performance issues, storage always seems to draw significant
attention. The goal of this chapter is to provide a quick understanding of how
a storage device should perform and easy ways to get a performance measurement
without expensive software. In addition to troubleshooting storage performance,
we touch on CPU bottlenecks and ways to find such events.

Chapter 5: Adding New Storage via SAN with Reference to PCMCIA and USB
Linux is moving out from under the desk and into the data center. An essential
feature of an enterprise computing platform is being able to access storage
on the SAN. This chapter provides a detailed walkthrough and examples of installing
and configuring Fibre Channel cards. We discuss driver issues, how the device
files work, and how to add LUNs.

Chapter 6: Disk Partitions and Filesystems
Master Boot Record (MBR) basics are explained, and examples are shown detailing
how bootloader programs such as LILO and GRUB manipulate the MBR. We explain
the partition table, and a lot of examples are given so that the reader will
understand how the disk is carved up into extended and logical partitions. Many
scenarios are provided explaining common disk and filesystem problems and their
solutions. After reading this chapter, the reader will understand not only what
MBA, LBA, extended partitions, and all the other buzzwords mean, but also how
they look on the disk and how to fix problems related to them.

Chapter 7: Device Failure and Replacement
This chapter explains identifying problems with hardware devices and how to
fix them. We begin with a discussion of supported devices. Whether a device
is supported by the Linux distribution is a good thing to know before spending
a lot of time trying to get it working. Next we show where to look for indications
of hardware problems. The reader will learn how to decipher the hexadecimal
error messages from dmesg and syslog. We explain how to use the lspci tool for
troubleshooting. When the error is understood, the next goal is to resolve the
device problem. We demonstrate techniques for determining what needs to be done
to fix device issues including SAN devices.

Chapter 8: Linux Processes: Structure, Hangs, and Core Dumps
Process management is the heart of the Linux kernel. A system administrator
should know what happens when a process is created to troubleshoot process issues.
This chapter explains process creation and provides a foundation for troubleshooting.
Linux is a multithreading kernel. The reader will learn how multithreading works
and what heavyweight and lightweight processes are. The reader also will learn
how to troubleshoot a process that seems to be hanging and not doing any work.
Core dumps are also covered. We show you how to learn which process dumped core
and why. This chapter details how cores are created and how to best utilize
them to understand the problem.

Chapter 9: Backup/Recovery
Creating good backups is one of if not the most important tasks a system administrator
must perform. This chapter